What do the terms “Lisp-1” and “Lisp-2” mean?
The terms Lisp-1 and Lisp-2 were invented by Kent Pitman and Richard Gabriel for use in their paper “Technical Issues of Separation in Function Cells and Value Cells”. In that paper Lisp-1 and Lisp-2 are defined as “two abstract dialects of Lisp”, presumed to be the same in all respects except for one, having to do with whether function names and variable names live in a single namespace or two distinct namespaces. A Lisp adopting the former strategy, such as Scheme, is a Lisp-1 and one adopting the latter, such as Common Lisp, is a Lisp-2.
